A pressure sensing device and method based on laser interference

Abstract

The application discloses a pressure sensor device and method based on laser interference, and relates to the technical field of pressure sensing, which comprises a laser driver, an adjustable frequency laser, a polarization maintaining coupler, a coherent coupler, a three-port single coupler, a pressure detector, a photoelectric detector and an upper computer demodulation system. The output end of the adjustable frequency laser is connected with the input end of the polarization maintaining coupler. The light beam generated by the laser driver is divided into two paths through the polarization maintaining coupler. The relationship between the coherent beat frequency and the optical path is obtained by using the laser coherence principle. The change of the optical path depends on the change intensity of the external pressure received by the pressure strain gauge. Then, the pressure value can be obtained. Since the measurement precision is high, the automatic metering of liquid ingredients can be realized. The automatic metering tank made of the sensor can be directly connected with the tank body through inlet and outlet pipelines, so that the equipment configuration in the industry is compact, the land occupation is small, the labor input is small, and the mechanical interference of weighing is eliminated.

Description

[0001] This invention relates to the field of pressure sensing technology, specifically to a pressure sensing device and method based on laser interferometry. Background Technology

[0002] For liquid measurement, the common methods are weighing liquids in tanks (containers) or using level gauges. These methods are inaccurate and cumbersome. For example, in industrial liquid batching (chemical, pharmaceutical, etc.), various liquids are often weighed in tanks before being poured into containers. This process is space-consuming, requires significant equipment and manpower, and often fails to meet accuracy requirements, affecting product quality. These methods limit the application of automation technology and hinder the development of related industrial sectors. To address the shortcomings of existing technologies, the purpose of this invention is to provide a pressure sensor with high measurement accuracy and simple operation, primarily used for measuring liquids and gases. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a pressure sensing device and method based on laser interferometry, which solves the problem of low measurement accuracy in existing devices.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a pressure sensing device based on laser interferometry, comprising a laser driver, a frequency-tunable laser, a polarization-maintaining coupler, a coherent coupler, a three-port unidirectional coupler, a pressure detector, a photodetector, and a host computer demodulation system. The output of the frequency-tunable laser is connected to the input of the polarization-maintaining coupler. The laser beam generated by the laser driver is split into two paths by the polarization-maintaining coupler. One path, a reference path, is transmitted via optical fiber to the first input of the coherent coupler. The other path, a measurement path, is connected to port 1 of the three-port unidirectional coupler. Port 2 of the three-port unidirectional coupler is connected to the pressure detector, and port 3 of the three-port unidirectional coupler is connected to the... The pressure detector generates a measurement path output to the second input terminal of the coherent coupler. The output terminal of the coherent coupler is connected to the photodetector and then to the host computer demodulation system. The pressure detector includes a pressure sensing spring, a housing, a measurement cavity, a beam shaper, and a reflector. The pressure sensing spring is in direct contact with the liquid. The polarization-maintaining coupler has a 6:4 power distribution, with 40% power for the reference path and 60% power for the measurement path. The beam splitting for the coherent coupler is 50:50. The housing and the pressure sensing spring are integrated. The housing is a mechanical structure that supports the measurement cavity, which consists of an outer cable shell, the beam shaper, the reflector, and the pressure sensing spring.

[0005] Preferably, the outer cable shell is a mechanical structure for installing armored cables.

[0006] Preferably, the reflector connected to the pressure-sensing spring is fixed to the measuring cavity, and a laser beam shaper for laser transmission and reception is set inside. The laser beam is emitted from the beam shaper, and a beam reflection is formed between the end face of the beam shaper and the surface of the reflector.

[0007] Preferably, the measuring cavity, the housing, and the pressure sensing spring are disposed at the optical fiber inlet end of the pressure detector.

[0008] Preferably, one port of the three-port unidirectional coupler is connected to the 60% laser output terminal of the polarization-maintaining coupler.

[0009] Preferably, the optical path of the three-port unidirectional coupler is from port 1 to port 2, and from port 2 to port 3. Otherwise, the beam is isolated and cannot flow in the opposite direction.

[0010] A pressure sensing method based on laser interferometry is disclosed. The output of the coherent coupler receives beat frequency signals from the reference path and the measurement path via a photodetector. By calculating the beat frequencies of the reference and measurement paths, the pressure value within the pressure detector is obtained. The frequency difference between the reference and measurement light is demodulated, and the change in optical path is obtained by analyzing this frequency difference. When the pressure changes, the pressure-sensing spring detects the pressure change, causing a change in the distance between the beam shaper and the lens. This changes the time it takes for the laser to return light within the pressure detector, thereby obtaining the pressure value of the pressure-sensing spring when the external pressure changes. Beneficial effects

[0011] This invention provides a pressure sensing device and method based on laser interferometry, which has the following beneficial effects: This invention utilizes the principle of laser coherence to obtain the relationship between coherent beat frequency and optical path. The change in optical path depends on the change in the intensity of external pressure on the pressure strain gauge, and thus the pressure value can be obtained. Due to its high measurement accuracy, it can realize automatic metering of liquid ingredients, and can be used to make an automatic metering tank. Its inlet and outlet pipes can be directly connected to the tank body, making the equipment configuration in industry compact, occupying less space, requiring less labor, eliminating mechanical interference in weighing, and realizing computer management of automatic weighing. The static measurement accuracy of liquid weight can reach 0.005%, and the gas pressure measurement accuracy can reach 0.02%. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the present invention.

[0013] Figure 2 This is a schematic diagram of the structure of the present invention.

[0014] In the diagram: 1. Laser driver; 2. Tunable laser; 3. Polarization-maintaining coupler; 4. Coherent coupler; 5. Three-port unidirectional coupler; 6. Pressure detector; 7. Photodetector; 8. Host computer demodulation system; 9. Pressure sensing spring; 10. Housing; 11. Measurement cavity; 12. Beam shaper; 13. Mirror; 14. Optical fiber; 15. Outer cable shell; 16. Reference path optical fiber. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Please see Figure 1-2This invention provides a technical solution: a pressure sensing device based on laser interferometry, comprising a laser driver 1, a frequency-tunable laser 2, a polarization-maintaining coupler 3, a coherent coupler 4, a three-port unidirectional coupler 5, a pressure detector 6, a photodetector 7, and a host computer demodulation system 8. The output terminal of the frequency-tunable laser 2 is connected to the input terminal of the polarization-maintaining coupler 3. The light beam generated by the laser driver 1 is split into two paths by the polarization-maintaining coupler 3. One path, a reference path fiber 16, is transmitted to the first input terminal of the coherent coupler 4. The other path, a measurement path, is connected to port 1 of the three-port unidirectional coupler 5. Port 2 of the three-port unidirectional coupler 5 is connected to the pressure detector 6. Port 3 of the three-port unidirectional coupler 5... The pressure detector 6 generates a measurement path output to the second input terminal of the coherent coupler 4. The output terminal of the coherent coupler 4 is connected to the photodetector 7 and then to the host computer demodulation system 8. The pressure detector 6 includes a pressure sensing spring 9, a housing 10, a measurement cavity 11, a beam shaper 12, and a reflector 13. The pressure sensing spring 9 is in direct contact with the liquid. The polarization-maintaining coupler 3 has a 6:4 power distribution, with 40% power for the reference path and 60% power for the measurement path. The beam splitting of the coherent coupler 4 is 50:50. The housing 10 is integrated with the pressure sensing spring 9. The housing 10 supports the outer cable shell 15 and the beam shaper 13. 2. The mechanical structure of the measuring cavity 11, consisting of a reflector 13 and a pressure-sensing spring 9; the outer cable shell 15 is a mechanical structure for installing armored cables; the reflector 13, connected to the pressure-sensing spring 9, is fixed to the measuring cavity 11, and a laser beam shaper 12 is set inside. The laser beam is emitted from the beam shaper 12, and a beam reflection is formed between the end face of the beam shaper 12 and the surface of the reflector 13; the measuring cavity 11, the shell 10, and the pressure-sensing spring 9 are located at the entrance end of the optical fiber 14 of the pressure detector 6; one port of the three-port unidirectional coupler 5 is connected to the 60% laser output end of the polarization-maintaining coupler 3; the optical path of the three-port unidirectional coupler 5 is from port 1 to... 2 ports, 2 ports to 3 ports, otherwise the beam is isolated and the beam cannot flow in reverse; a pressure sensing method based on laser interference, the output of the coherent coupler 4 obtains the beat frequency signals of the reference path and the measurement path through the photodetector 7, by calculating the beat frequency of the reference path and the measurement path, the pressure value in the pressure detector 6 is obtained, the frequency difference between the reference light and the measurement light is demodulated, and the change in optical path is obtained by the frequency difference between the reference path and the measurement path, when the pressure changes, the pressure sensing spring 9 knows the pressure change, so that the distance between the beam shaper 12 and the lens changes, so that the time for the laser to generate return light in the pressure detector 6 changes, thereby obtaining the pressure value of the pressure sensing spring 9 when the external pressure changes.

[0017] Those skilled in the art can connect the components in this case sequentially. The specific connection and operation sequence should refer to the working principle described below. The detailed connection methods are well-known technologies in the field. The working principle and process are mainly described below.

[0018] Example: By controlling the frequency-modulated laser driver 1 and the frequency-tunable laser 2, the beam generated by the frequency-tunable laser 2 is split into two paths by the polarization-maintaining coupler 3. One path passes through the reference fiber 14 to the first input terminal of the coherent coupler 4, serving as the reference path for frequency and phase demodulation. The other path passes through the pressure detector 6 to generate the measurement path output to the second input terminal of the coherent coupler 4. The output terminal of the coherent coupler 4 obtains the beat frequency signals of the reference path and the measurement path through the photodetector 7. By calculating the beat frequencies of the first and second paths, the pressure value inside the pressure detector 6 is obtained. Based on the physical relationship between the pressure value and the measured object, the required physical value can be obtained. Since the pressure sensing spring 9 inside the pressure detector 6 acts directly on the liquid, when the measured liquid level changes, the liquid pressure changes, causing the liquid... The pressure-sensing spring 9 senses a pressure change, causing the reflector 13 to move and its position to change. This alters the distance between the beam shaper 12 and the reflector 13, changing the beat frequency of the interference signal. This enables fiber optic interference level measurement, allowing for precise calculation of liquid level and weight by measuring liquid pressure. It can also calculate gas molar volume by measuring gas pressure. Applications include automatic metering of liquid ingredients and the fabrication of automatic metering tanks with inlet and outlet pipes directly connected to the tank body. This results in compact equipment configurations in industrial settings, requiring less space and labor, eliminating mechanical interference in weighing, and enabling computerized automatic weighing management. The static measurement accuracy for liquid weight reaches 0.005%, and for gas pressure measurement, it reaches 0.02%, effectively improving measurement accuracy.

Claims

1. A pressure sensing device based on laser interferometry, comprising a laser driver (1), a frequency-tunable laser (2), a polarization-maintaining coupler (3), a coherent coupler (4), a three-port unidirectional coupler (5), a pressure detector (6), a photodetector (7), and a host computer demodulation system (8), characterized in that, The output of the tunable laser (2) is connected to the input of the polarization-maintaining coupler (3). The beam generated by the laser driver (1) is split into two paths by the polarization-maintaining coupler (3). One path, a reference fiber (16), is transmitted to the first input of the coherent coupler (4). The other path, a measurement path, is connected to port 1 of the three-port unidirectional coupler (5). Port 2 of the three-port unidirectional coupler (5) is connected to the pressure detector (6). Port 3 of the three-port unidirectional coupler (5) is connected to the second input of the coherent coupler (4). The pressure detector (6) generates a measurement path output to the second input of the coherent coupler (4). The output of the coherent coupler (4) is connected to the photodetector (7). Then connected to the host computer demodulation system (8), the pressure detector (6) includes a pressure sensing spring (9), a housing (10), a measuring cavity (11), a beam shaper (12) and a reflector (13). The pressure sensing spring (9) is in direct contact with the liquid. The polarization maintaining coupler (3) has a 6:4 power distribution, with 40% power for the reference path and 60% power for the measuring path. The coherent coupler (4) has a 50:50 beam splitting. The housing (10) and the pressure sensing spring (9) are integrated. The housing (10) is a mechanical structure that supports the measuring cavity (11) composed of the outer cable shell (15), the beam shaper (12), the reflector (13) and the pressure sensing spring (9).

2. The pressure sensing device based on laser interferometry according to claim 1, characterized in that, The outer cable shell (15) is a mechanical structure for installing armored cables.

3. The pressure sensing device based on laser interferometry according to claim 1, characterized in that, The reflector (13) connected to the pressure sensing spring (9) is fixed to the measuring cavity (11), and a laser beam shaper (12) for laser transmission and reception is set inside. The laser beam is emitted from the beam shaper (12) and a beam reflection is formed between the end face of the beam shaper (12) and the surface of the reflector (13).

4. The pressure sensing device based on laser interferometry according to claim 1, characterized in that, The measuring cavity (11), the housing (10), and the pressure sensing spring (9) are disposed at the optical fiber (14) inlet end of the pressure detector (6).

5. A pressure sensing device based on laser interferometry according to claim 1, characterized in that, One port of the three-port unidirectional coupler (5) is connected to the 60% laser output terminal of the polarization-maintaining coupler (3).

6. The pressure sensing device based on laser interferometry according to claim 1, characterized in that, The optical path of the three-port unidirectional coupler (5) is from port 1 to port 2 and from port 2 to port 3. Otherwise, the beam is isolated and the beam cannot flow in the opposite direction.

7. A pressure sensing method based on laser interferometry, using the pressure sensing device according to any one of claims 1-6, characterized in that, The output of the coherent coupler (4) obtains the beat frequency signals of the reference path and the measurement path through the photodetector (7). By calculating the beat frequency of the reference path and the measurement path, the pressure value in the pressure detector (6) is obtained. The frequency difference between the reference light and the measurement light is demodulated, and the change in optical path is obtained by corresponding the frequency difference between the reference path and the measurement path. When the pressure changes, the pressure sensing spring (9) knows the pressure change, which changes the distance between the beam shaper (12) and the reflector (13), and changes the time when the laser generates the return light in the pressure detector (6), thereby obtaining the pressure value of the pressure sensing spring (9) when the external pressure changes.

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